/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jmx.access;

import java.io.IOException;
import java.net.MalformedURLException;
import java.util.Arrays;
import java.util.Map;
import javax.management.MBeanServerConnection;
import javax.management.ObjectName;
import javax.management.remote.JMXServiceURL;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jmx.JmxException;
import org.springframework.jmx.MBeanServerNotFoundException;
import org.springframework.jmx.support.NotificationListenerHolder;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;

/**
 * Registrar object that associates a specific {@link javax.management.NotificationListener}
 * with one or more MBeans in an {@link javax.management.MBeanServer}
 * (typically via a {@link javax.management.MBeanServerConnection}).
 *
 * @author Juergen Hoeller
 * @see #setServer
 * @see #setMappedObjectNames
 * @see #setNotificationListener
 * @since 2.5.2
 */
public class NotificationListenerRegistrar extends NotificationListenerHolder
        implements InitializingBean, DisposableBean {

    /**
     * Logger available to subclasses.
     */
    protected final Log logger = LogFactory.getLog(getClass());

    private final ConnectorDelegate connector = new ConnectorDelegate();

    @Nullable
    private MBeanServerConnection server;

    @Nullable
    private JMXServiceURL serviceUrl;

    @Nullable
    private Map<String, ?> environment;

    @Nullable
    private String agentId;

    @Nullable
    private ObjectName[] actualObjectNames;


    /**
     * Set the {@code MBeanServerConnection} used to connect to the
     * MBean which all invocations are routed to.
     */
    public void setServer(MBeanServerConnection server) {
        this.server = server;
    }

    /**
     * Specify the environment for the JMX connector.
     *
     * @see javax.management.remote.JMXConnectorFactory#connect(javax.management.remote.JMXServiceURL, java.util.Map)
     */
    public void setEnvironment(@Nullable Map<String, ?> environment) {
        this.environment = environment;
    }

    /**
     * Allow Map access to the environment to be set for the connector,
     * with the option to add or override specific entries.
     * <p>Useful for specifying entries directly, for example via
     * "environment[myKey]". This is particularly useful for
     * adding or overriding entries in child bean definitions.
     */
    @Nullable
    public Map<String, ?> getEnvironment() {
        return this.environment;
    }

    /**
     * Set the service URL of the remote {@code MBeanServer}.
     */
    public void setServiceUrl(String url) throws MalformedURLException {
        this.serviceUrl = new JMXServiceURL(url);
    }

    /**
     * Set the agent id of the {@code MBeanServer} to locate.
     * <p>Default is none. If specified, this will result in an
     * attempt being made to locate the attendant MBeanServer, unless
     * the {@link #setServiceUrl "serviceUrl"} property has been set.
     *
     * @see javax.management.MBeanServerFactory#findMBeanServer(String)
     * <p>Specifying the empty String indicates the platform MBeanServer.
     */
    public void setAgentId(String agentId) {
        this.agentId = agentId;
    }


    @Override
    public void afterPropertiesSet() {
        if (getNotificationListener() == null) {
            throw new IllegalArgumentException("Property 'notificationListener' is required");
        }
        if (CollectionUtils.isEmpty(this.mappedObjectNames)) {
            throw new IllegalArgumentException("Property 'mappedObjectName' is required");
        }
        prepare();
    }

    /**
     * Registers the specified {@code NotificationListener}.
     * <p>Ensures that an {@code MBeanServerConnection} is configured and attempts
     * to detect a local connection if one is not supplied.
     */
    public void prepare() {
        if (this.server == null) {
            this.server = this.connector.connect(this.serviceUrl, this.environment, this.agentId);
        }
        try {
            this.actualObjectNames = getResolvedObjectNames();
            if (this.actualObjectNames != null) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Registering NotificationListener for MBeans " + Arrays.asList(this.actualObjectNames));
                }
                for (ObjectName actualObjectName : this.actualObjectNames) {
                    this.server.addNotificationListener(
                            actualObjectName, getNotificationListener(), getNotificationFilter(), getHandback());
                }
            }
        } catch (IOException ex) {
            throw new MBeanServerNotFoundException(
                    "Could not connect to remote MBeanServer at URL [" + this.serviceUrl + "]", ex);
        } catch (Exception ex) {
            throw new JmxException("Unable to register NotificationListener", ex);
        }
    }

    /**
     * Unregisters the specified {@code NotificationListener}.
     */
    @Override
    public void destroy() {
        try {
            if (this.server != null && this.actualObjectNames != null) {
                for (ObjectName actualObjectName : this.actualObjectNames) {
                    try {
                        this.server.removeNotificationListener(
                                actualObjectName, getNotificationListener(), getNotificationFilter(), getHandback());
                    } catch (Exception ex) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("Unable to unregister NotificationListener", ex);
                        }
                    }
                }
            }
        } finally {
            this.connector.close();
        }
    }

}
